Disk drives are information storage devices that use magnetic media to store data. Consumers are constantly desiring greater storage capacity for such disk drive devices, as well as faster and more accurate reading and writing operations. Thus, disk drive manufacturers have continued to develop higher capacity disk drives by, for example, increasing the density of the information tracks on the disks by using a narrower track width and/or a narrower track pitch. However, each increase in track density requires that the disk drive device have a corresponding increase in the positional control of the read/write head in order to enable quick and accurate reading and writing operations using for the higher density disks. As track density increases, it becomes more and more difficult using known technology to quickly and accurately position the read/write head over the desired information tracks on the storage media. Thus, disk drive manufacturers are constantly seeking ways to improve the positional control of the read/write head in order to take advantage of the continual increases in track density.
As a way to improve the positional control of the read/write head, Various dual-stage actuator systems have been developed in the past for the purpose of increasing the speed and fine tuning the position of the read/write head over the desired tracks on high density storage media. Such dual-stage actuator systems typically include a primary voice-coil motor (VCM) actuator and a secondary micro-actuator, such as a PZT micro-actuator. The VCM actuator is controlled by a servo control system that rotates the actuator arm that supports the read/write head to position the read/write head over the desired information track on the storage media. The PZT micro-actuator is used in conjunction with the VCM actuator for the purpose of increasing the positioning speed and fine tuning the exact position of the read/write head over the desired track. Thus, the VCM actuator makes larger adjustments to the position of the read/write head, while the PZT micro-actuator makes smaller adjustments that fine tune the position of the read/write head relative to the storage media. In conjunction, the VCM actuator and the PZT micro-actuator enable information to be efficiently and accurately written to and read from high density storage media.
FIG. 1 a illustrates a portion of a conventional disk drive unit and shows a magnetic disk 101 mounted on a spindle motor 102 for spinning the disk 101. A voice coil motor arm 104 carries a HGA 100 that includes a slider 103, incorporating a read/write head. A voice-coil motor (VCM) (not shown) is provided for controlling the motion of the motor arm 104 and, in turn, controlling the slider 103 to move from track to track across the surface of the disk 101, thereby enabling the read/write head to read data from or write data to the disk 101. In operation, a lift force is generated by the aerodynamic interaction between the slider 103 and the spinning magnetic disk 101. The lift force is opposed by equal and opposite spring forces applied by a suspension of the HGA such that a predetermined flying height above the surface of the spinning disk 101 is maintained over a full radial stroke of the motor arm 104.
FIG. 1b illustrates the HGA 100 of the conventional disk drive device of FIG. 1a. FIG. 1c is an enlarged, partial side perspective view of the HGA 100 of FIG. 1b. The HGA 100 includes the slider 103, a PZT micro-actuator 105, and a suspension 110 to support the slider 103 and the PZT micro-actuator 105. The suspension 110 comprises a base plate 113, a hinge 112, a load beam 115, and a flexure 114. The flexure 114 provides a suspension tongue 328 for supporting the slider 103 and the PZT micro-actuator 105 on the suspension 110. The load beam 115 has a dimple 329 formed thereon to support the suspension tongue 328. The PZT micro-actuator 105, as described above, is provided in order to improve the positional control of the slider 103. More particularly, the PZT micro-actuator 105 corrects the displacement of the slider 103 on a much smaller scale, as compared to the VCM, in order to compensate for the resonance tolerance of the VCM and the head suspension assembly. The PZT micro-actuator 105 enables, for example, the use of a smaller recording track pitch, and can increase the “tracks-per-inch” (TPI) value by 50% for the disk drive unit, as well as provides an advantageous reduction in the head seeking and settling time. Thus, the PZT micro-actuator 105 enables the disk drive device to have a significant increase in the surface recording density of the information storage disks used therein.
With reference to FIGS. 1b to 1d, the PZT micro-actuator 105 includes a ceramic U-shaped frame which has a bottom arm 137 and two ceramic beams or side arms 107 that hold the slider 103 there-between. Each ceramic beam 107 has a PZT element 208 thereon. The PZT micro-actuator 105 is physically coupled to the flexure 114. Three electrical connection balls 109 (gold ball bonding or solder ball bonding, GBB or SBB) are provided to couple the micro-actuator 105 to suspension inner traces 910 located at the side of each of the ceramic beams 107 of the micro-actuator 105. In addition, there are four metal balls 108 (GBB or SBB) for coupling the slider 103 to suspension outer traces 190 located at the side of each of the ceramic beams 107 of the micro-actuator 105. The slider 103 is partially bonded with the two ceramic beams 107 at two predetermined positions 106 by epoxy 112. This bonding makes the movement of the slider 103 dependent on the movement of the ceramic beams 107 of the micro-actuator 105. When power is supplied through the suspension traces 910, the PZT elements 208 expand or contract to cause the two ceramic beams 107 of the U-shape micro-actuator frame to deform, thereby making the slider 103 move on the track of the disk in order to fine tune the position of the read/write head. In this manner, controlled displacement of the slider 103 can be achieved for fine positional tuning. Also, a parallel gap 398 is formed between the micro-actuator 105 and the suspension tongue 328 in order to ensure free movement of the slider 103.
As is known to all, with the quickly increasing of the HDD capability, the actual HDD selling prices becomes lower and lower. The manufacturer are continue to develop methods to cut down the material cost in order to meet the market. A typically example is make the head slider smaller and smaller, etc. from 100% slider to 50% slider. The current is 30% slider and everyone is focusing on 20% slider now. Since reduction of the slider size results in reduction of the size of the air bearing surface (ABS) side of the slider, while a big capacity HDD must have a lower and lower slider flying height, so it is a big challenge on the design for ABS pattern of the slider and the static parameter of the suspension, for example, the stiffness of the suspension. Due to limitation in ABS design, a lower and lower stiffness is required for the suspension, for instance, the pitch stiffness of the suspension is less than 0.75 μN/mm and the roll stiffness of the suspension is less than 0.6 μN/mm. To achieve such a low stiffness, the flexure of the suspension has reduced its thickness from traditional 25 μm to 22 μm or thinner.
However, the thickness reduction of the flexure may cause a problem on slider dynamic performance, for example, the suspension tongue may be deformed, such a problem may become serious especially under circumstance when a micro-actuator is applied. FIG. 1e is a diagrammatic view showing the deformation of the suspension tongue 328 under the support of the dimple 329 of the load beam 115. As shown in FIG. 1e, the free end of the suspension tongue 328 is bent toward the micro-actuator 105, which will reduce the gap 398 between the micro-actuator 105 and the suspension tongue 328, even cause an interference between the micro-actuator 105 and the suspension tongue 328, which further deteriorates the dynamic performance of the slider 103, such as position adjustment performance.
Hence, it is desired to provide a lower stiffness suspension, a head gimbal assembly (HGA), and a disk drive unit with such suspension that are suitable for small size slider and micro-actuator to solve the above-mentioned problems.